This API supports the product infrastructure and is not intended to be used directly from your code.
Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)

Apply this attribute to the entry point method (the Main() method in C# and Visual Basic). It has no effect on other methods. To set the apartment state of threads you start in your code, use the Thread::SetApartmentState or Thread::TrySetApartmentState method before starting the thread.

COM threading models only apply to applications that use COM interop. The COM threading model can be set to single-threaded apartment or multithreaded apartment. The application thread is only initialized for COM interop if the thread actually makes a call to a COM component. If COM interop is not used, then the thread is not initialized, and the MTAThreadAttribute attribute, if it is present, has no effect.

Starting with the .NET Framework version 2.0, the default threading model for COM interop depends on the language in which you are developing your application, as the following table shows.

Some of the cases in which you want to use the MTAThreadAttribute attribute to explicitly set the threading model to multithreaded apartment include the following:

You're developing a Visual Basic app that calls to a C# library that in turn relies on COM interop. Because the multithreaded apartment model is the default for C#, you should change your app's threading model to multithreaded by using the MTAThreadAttribute attribute.

Your application makes calls to COM components that use the multithreaded apartment model.